Narrowband Internet of Things (Narrowband Internet of Things, NB-IoT) communication is characterized by a low data rate, low latency sensitivity, low complexity, a large quantity of terminals (User Equipment, UE), and the like. Two uplink transmission modes are defined in NB-IoT: single-tone transmission (single-tone transmission) and multi-tone transmission (multi-tone transmission). In single-tone transmission, two types of subcarrier spacings are used: 3.75 kHz and 15 kHz. In multi-tone transmission, a 15 kHz subcarrier spacing is used.
In a Long Term Evolution (Long Term Evolution, LTE) or LTE-advanced (LTE-Advanced, LTE-A) system, a 15 kHz subcarrier spacing is used in both single-tone transmission and multi-tone transmission. In other words, LTE/LTE-A supports only one type of uplink subcarrier spacing.
A subcarrier spacing is a basic parameter in a communications system. In LTE and LTE-A, because only one type of uplink subcarrier spacing is defined for data transmission, an eNodeB and a terminal do not need to indicate their respective supported uplink subcarrier spacings to each other. However, in an NB-IoT system, because two types of subcarrier spacings are defined for single-tone transmission, if an uplink subcarrier spacing used by UE is inconsistent with a subcarrier spacing supported by a base station, the base station cannot correctly demodulate an uplink signal of the terminal.